Archive ouverte HAL – Characterizing Thermal Mixing Dynamic Nuclear Polarization via Cross-Talk between Spin Reservoirs

David Guarin ¹ Sina Marhabaie ¹ Alberto Rosso ^{1, 2} Daniel Abergel ¹ Geoffrey Bodenhausen ¹ Konstantin Ivanov ³ Dennis Kurzbach ¹

Journal of Physical Chemistry Letters, American Chemical Society, 2017, 8 (22), pp.5531-5536. 〈10.1021/acs.jpclett.7b02233〉

Dynamic nuclear polarization (DNP) embraces a family of methods to increase signal intensities in nuclear magnetic resonance (NMR) spectroscopy. Despite extensive theoretical work that allows one to distinguish at least five distinct mechanisms, it remains challenging to determine the relative weights of the processes that are responsible for DNP in state-of-the-art experiments operating with stable organic radicals like nitroxides at high magnetic fields and low temperatures. Specifically, determining experimental conditions where DNP involves thermal mixing, which denotes a spontaneous heat exchange between different spin reservoirs, remains challenging. We propose an experimental approach to ascertain the prevalence of the thermal mixing regime by monitoring characteristic signature properties of the time evolution of the hyperpolarization. We find that thermal mixing is the dominant DNP mechanism at high nitroxide radical concentrations, while a mixture of different mechanisms prevails at lower concentrations.

• 1. LBM UMR 7203 – Laboratoire des biomolécules
• 2. LPTMS – Laboratoire de Physique Théorique et Modèles Statistiques
• 3. NSU – Novosibirsk State University